By Neal Henderson MS, CSCS

Competing effectively in Ironman requires equal parts physical, mental, and nutritional strategies.  Many athletes place too much emphasis on the physical and mental preparation and go into the race without a solid plan for their nutritional needs.  Because an Ironman race can take between 8 and 17 hours to complete, there will be some differences in the strategies employed by top elite finishers competing for the win and those athletes just aiming to complete the distance.  The key areas that need to be planned regarding your nutrition race plan include: hydration & electrolyte balance, and energy intake.

Hydration & Electrolytes – Your GI system functions best with a consistent fluid intake, rather than emptying and refilling.  The amount of fluid that you need will depend on environmental conditions (heat & humidity), your pace/effort (the faster you go, the more heat you produce – hence the more you sweat to stay cool), and your personal sweat rate.  I have seen fluid intake recommendations from 4-8 ounces of per hour to several liters per hour.  In reality, the only way to know your personal fluid intake needs is to perform very precise laboratory sweat rate testing in environmental conditions and effort equal to your goal pace, or to estimate those needs using pre-post body weight measurements in similar conditions as your race.  See this article for more on determining sweat rate and determining electrolyte needs.  Typically, long-distance competitions such as Ironman is where electrolyte balance and fluid intake must be balanced.  A condition know as hyponatremia (low blood sodium) results when too much fluid is ingested without adequate sodium.  This condition is potentially fatal, so it is extremely important to maintain appropriate electrolyte content with your fluid intake.  Generally speaking, starting at a goal intake of 16-32 ounces of water per hour and a concentration of 800 mg of sodium per liter of fluid (33.7 ounces) is a good starting point for many athletes to begin with.

Energy Intake – Because an Ironman takes many hours to complete, it is virtually impossible to complete without energy intake.  Your body can only store a limited amount of glycogen (storage form of carbohydrates), and this supply can become exhausted in just a couple of hours.  Fat will also be used as a fuel during exercise, but even a very lean athlete has adequate fat stores to last them through several Ironman races run back-to-back, so fat intake is not recommended.  Also, protein use during exercise is extremely low, except in the case of starvation, so protein intake during your race is not going to be a major concern.  Your pacing strategy will also affect energy intake needs, as a lower intensity of effort yields lower total calorie use and more equal use of carbohydrate and fat.  As the intensity of your effort increases, your total energy expenditure rate increases, as does the portion of carbohydrate used.  A well equipped exercise physiology laboratory can actually help you determine the amount and composition of fuel that your body is using during exercise using indirect calorimetry.   This test known as your substrate utilization can help determine how much fat vs carbohydrates your body uses at a given effort and is the only real way to determine how many carbohydrate calories you need to replace during your Ironman.  Again, the general recommendations for carbohydrate intake during exercise can vary from 25-30 grams per hour up to 120+ grams per hour depending on your training status, pace, and tolerance.  Your energy intake should primarily come from carbohydrate during exercise, with small amounts of both protein or free form amino acids.  Both protein and fat require much longer to be digested and can cause GI distress during exercise when blood flow is required by more than just the gut.   Consuming free form amino acids instead of complete proteins should be considered as they are easier to absorb.  See this article for guidance on Ironman fueling using First Endurance products.

Finally, you should also pay attention to the following ideas that can help you avoid gastric distress.

1. Pacing – If you go harder than you have planned or trained to go, your gut’s ability to process nutrition decreases as the intensity of your exercise increases – and your use of energy in total, and especially in carbohydrate amount goes up!  This issue is the primary cause of GI distress and poor race performance in many athletes that I have worked with over the past 15 years.

2. Caffeine – Pay attention to the labels on your race-day products…as many items contain caffeine.  In moderation, caffeine can be a good thing for many endurance athletes – but in high amounts it is definitely associated with GI stress.

3. Consistency – Be sure to use only products that you have successfully used in training.  In Ironman distance races, its not always possible to carry all of the fluids that you need – even using special needs bags.  To deal with this problem many years ago when I raced Ironman events, I mixed concentrated bottles of my preferred sports drink.  I then marked off with a sharpie pen on the clear bottle the right amount of concentrate to mix with each bottle of water that I got from the neutral aid stations, and could mix my drink in a front mounted water bottle throughout the race.

4. Flexibility – Be sure that you can adjust your intake and pace for the race based on the conditions.  Hot/cold/wind/etc. can all significantly affect how long you are on course – and the effort required to go a given pace.  Be sure that you adapt your intake to match the conditions on the day.  5. Medications – Beware of taking medications during the race.  Not only can some medicines cause dangerous stresses on your organs during exercise, many can also do a number on your stomach.  If you can’t train and compete without taking medicine for pain, you might want to re-consider whether what you are doing is healthy for you.  Ultimately, training for sports and competing in Ironman races is about living a healthy lifestyle.